2 answers

I’m not sure if there are any specific best practices I can personally offer – I do know that this response rate calculation is not currently available in SG across multiple campaigns.

I think the best current option here may be to download the status log file for each campaign (‘Export Contacts with Send Status’ on the Contacts page of an email campaign).

You can then combine the status log files from multiple campaigns into one excel spreadsheet. The status log files have data on the sends (columns E-G) and also has a Response ID column (I). One way of going about this is to total the cells in column I that have data and divide this by the number of data pieces in column G for example.